I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
January 15, 1931
buret capped, and weighed. The whole operation should be performed quickly. The loss in weight of the buret, subtracted from the calibration value, gives the weight of ether displaced by the specimen. Dividing the weight of displaced ether by its density of 0.719 gram per cubic centimeter gives the displaced volume of the specimen and a simple calculation serves to give the required density. Temperature corrections for the expansion of the glass tube over the ordinary range of working temperatures is not required as it is less than the other errors involved. Results
The results obtained on various substances are shown in Tables I to IV. The values by the pycnometer method were determined a t 15” C. on large samples of the same material as used for the other determinations. The determinations by the ether method were done at approximately 15” C. Clerici’s solution was used as a check in the case of the cut gems, the same gem being used in both determinations. No difficulty was experienced in checking against the pycnometer in the case of the larger samples. I n the case of the cut gems the values do not check quite so
11
closely but the ether method result is probably the one nearest to the actual value. The individual determinations of the extremely small samples vary more from the true value than do those in which a larger volume of liquid is displaced, but the average value of a series is generally quite satisfactory. The result with cork, noted on Table IV, shows that substances lighter than ether give concordant checks with the values obtained by other procedures. The applicability of this method to large and small samples, and to substances lighter than the displacing liquid is very satisfactory. The procedure is rapid and the results obtained check with those obtained by other methods. Literature Cited (1) Caley, IND. ENQ.CHEX.,Anal. Ed., 2, 177 (1930). (2) Clerici, A t f i . accad. Lincei, 16, 187 (1907). (3) Friedman and LaMer, IND. ENG.CHEM.,Anal. Ed., 2, 54 (1930). (4) Kraus and Holden, “Gems and Gem Materials,” p. 26, McGraw-Hill, 1925.
:;
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~ ~ ~ ~ ~ ~ ; , A (1927) & ~ ~ ~ ~ ~ (7) Weinschenk and Clark, “Petrographic Methods,” p. 179, McGraw-Hill, 1912.
Arc Spectrographic Estimation of Chromium in Ruby’ Jacob Papish and Wm. J. O’Leary DEPARTMENT OF CHEMSTRY, CORNELL UNIVERSITY, ITHACA, N Y.
ECAUSE synthetic ruThe persistence of the arc spectral lines of chromium alyzed by titration with 0.1 bies are colored red by as conditioned by concentration of the element has 1V potassium permanganate the addition of from been studied in the range between AX 5785.8 and 3120.4 a n d FeS04.(NH4)1S04.6H10 A. The study was extended to chromium in a mix- in the usual way and was 2 to 4 per cent chromic oxide, it has been assumed that the ture of fused chromic oxide and alumina, and it was found to contain 0.0099 gram color of natural rubies i8 also observed that the sensitivity of the spectral reaction of chromium per cubic tendue to this substance. The was much greater in the case of chromium in fused timeter. Because the error presence of chromium in rualumina than in the case of chromium when arcked as was only 1 per cent of the chromic acid. The method was applied to the estimabies has long been known ( 8 ) ; i n t e n d e d amount, and beit is also known that there is tion of chromium in rubies. cause the subsequent dilunot as much chromium in t i o n s would make it still the natural gem as there is in the synthetic. According to more negligible, the value 0,0099 gram was designated as Wohler and Kraatz-Koschlau (9) the chromium in natural 0.01 gram of chromium per cubic centimeter. This solution rubies is analytically not determinable, as it is present in was diluted in volumetric flasks to give a series of solutions very small amounts. Doelter (1) also states that the containing, respectively, 0.01, 0.001, 0.0001, 0.00001, and amount of chromium in natural rubies is so small that it 0.000001 gram of chromium per cubic centimeter. A one-tenth cannot be determined quantitatively. Wild and Klemm (8) cubic centimeter sample of each of these solutions, measured examined the emission spectra of rubies from Siam and from a calibrated capillary pipet, each sample containing, Montana, using a carbon arc, and compared them with that respectively, 1.0, 0.1, 0.01, 0.001, and 0.0001 milligram of of a synthetic ruby. They found that while all of them chromium, was subjected to arc spectral excitation between showed lines due to chromium, the synthetic ruby contained graphite electrodes 7 mm. in diameter, on 110-volt direct more chromium than natural ones, as evidenced by more current, using about 600 watts. The lower electrode was intense lines. Theyo report that the chromium lines XX made the anode, and the samples were placed thereon. The 3593.5 and 3578.7 A. were missing in the spectrogram of spectrograph employed was of the Littrow auto-collimating the Siam ruby, and X 2653.7 A. was missing in the spectro- type, fitted with a 30-degree quartz prism, and the spectra grams of the rubies from Siam and Montana. were photographed on d. c. ortho plates.2 In the present investigation, an arc spectrographic method Chromium yields a large number of arc lines in the optical was adopted to estimate the amount of chromium in naturally spectral range that decrease in intensity and persistence occurring rubies. The experimental procedure has been with diminishing amounts of the element under excitation. described elsewhere (5, 6, 7 ) ,and will be outlined only briefly The most sensitive of these lines between XX 5785.5 and 3120.4 here. h., with their persistence at varying concentrations, are listed in Table I. In this table, (v) is used to designate that a Persistence of Arc Spectral Lines of Chromium line is visible, (f) that it is faint, and (vf) that it is very faint. A solution was prepared containing 1.923 grams of chro- For the purpose of spectrographic estimation of small quanmium trioxide in 100 cc. of aqueous solutior. This was an- tities the following lines were found most suitable: AX 5208.4,
B
Received August 22, 1930.
2
Made by Eastman Kodak Company, Rochester, N. Y.
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Vol. 3, No. 1
ANALYTICAL EDITION
12
5206.0, 5204.6, 4626.2, 4622.5,4619.5, 4616.1,4613.3, 4546.0, 4544.6, 4540.7, 4535.7, 4530.7, 4289.7, 4274.8, 4254.3, 3605.3, 3593.5, and 3346.7 A.
Table 11-Chromium Content of Synthetic Rubies
No.
1
Table I-Persistence
x 5785.8 5785.0 5783.9 5783.1 6781.8 5781.2 5409.8 5348.3 5345.8 5328.3 5300.7 5298.3 5297.3 5296.7 5265.7 5264.2 5208.4 5200.0 5204.0 4052.2 4640.2 4020.2 4622.6 4619.5 4610.1 4613.3 4540.0 4544.6 4540.7 4535.7 4530.7 4371.3 4363.1 4351.8 4361.1 4344.5 4339.7 4339.5 4337.6 4289.7 4274.8 4254.3 3976.7 3969.8 3903.7 3941.5 3928.7 3921.0 3919.2 3910.3 3908,8 3894.1 3743 9 3743:0] 3639.8 3636.6 3605.3 3593.5 3578.7 3433.6 3340.7 3132.1 3120.4
i 1
of Arc SDectral Lines of C h r o m i u m MILLIGRAMSOF CHROMIUM AS Cr0.n 1.0 0.1 0.01 0,001
V
f f f
f
V
f
V V V V V V V V V
f f
V
V V V
V V
f f
f vf vf
VI
vf vf vf
V V V V V V V V V V
vf vf vf
V
V
vf vf
vf V V V
V
V
V V V V V V V V V V V V
V V V V V
V V V
f
f f
f
V V
vf V V V V V V V V V
vf
vf V V V V V V V
DETERMINED
%
Deep purplish red Deep red Pale pink Very faint pink White
2 3 4 5
1.84 0.944 0.092 0.009 0.0009
Table 111-Persistance of Arc S ectral Lines of C h r o m i u m i n Fused Afumina MILLIGRAMS OB CHROMIUM (AS CmOs) IN FUSED ALUMINA x 0.05 0.006 0.0005 0.00005 5785.8 5785.0 5783.9 5783.1 V 5781.8 5781.2 5409.8 V 5348.3 V 5345.8 V 5328,3 V
V
V V V V
CHROMIUM
COLOR
vf vf
5297.3 5296.7 5265.7 5264.2 5208.4 5206.0 5204.6 4652.2 4646.2 4626.2 4622.5 4619.5 4616.1 4613.3 4546.0 4544.6 4540.7 4535.7 4530.7 4371.3 4363.1 4351 8 4351 1 4344.5
1 %:: 1 4337.6 4289.7 4274.8 4254.3 3976.7 3969.8 3963.7 3941.5 3928.7 3921.0 3919.2 3916.3 3908.8 3894.1
In order to duplicate the conditions under which the natural rubies were to be examined, a number of synthetic rubies were prepared as follows: An aqueous solution of ammonium chromium alum was prepared, containing approximately 0.01 gram of chromium per cubic centimeter. Definite portions of this solution (10, 5, and 0.5 cc.) were added to 44-gram portions of ammonium alum dissolved in water. The ammonium chromium alum solution was further diluted, and of this new solution, containing approximately 0.0001 gram of chromium per cubic centimeter, a 5-cc. and 0.5-cc. portion were added to 44-gram portions of ammonium alum dissolved in water. These amounts were calculated to yield rubies containing 2, 1, 0.1, 0.01, and 0.001 per cent chromium. The combined hydrous oxides of aluminum and chromium were then precipitated from each of the five mixtures by means of ammonium hydroxide, were filtered off, washed free of sulfate, and were ignited to aluminum oxide and chromic oxide. The hydrous oxides were precipitated together to ensure an intimate mixture with consequent uniformity of composition in the rubies.
V V V V V V . V V V V V V V V V V
V V V V
V V
V
V
V
V
V
V
V V
V
V V V V V V V V V V
V V
V V V
f f
f
Y
f
V
vf
vf
Arc Spectrographic Estimation of Chromium in Synthetic Rubies
t
V
3639.8 3636.6 3605.3 3593.5 3578.7 3433.0 3346.7 3132.1 3120.4
V V V V V V V V V
vf vf V V V V V
vf vf
vf
V V
Portions of each of the powdered mixed oxides were then put in a shallow graphite crucible, about 2.5 om. in outside diameter, and the crucib:e was placed between the graphite electrodes of a horizontal arc furnace drawing 110 volts and approximately 300 amperes direct current. Separate crucibles were used for the different concentrations of chromium. The arc was then made to play on the sides of the crucible till the powdered oxides fused, this process usually requiring from 2 to 5 minutes. The resulting rubies were opaque, spherical in shape, and weighed 0.1 to 0.15 gram, Several grams of each of the different rubies were obtained in this way. The color intensity of these rubies varied, as was to be expected, directly with their chromium content. The rubies were broken and examined microscopically; they were completely and homogeneously fused, were uniformly colored, and were crystalline aggregates, consisting of rhombohedra parallel to each other. This fact accounted in part for their opacity. They were then analyzed so as to determine the
January 15,1931
I N D U S T R I A L A N D ENGINEERING CHEMIXTRY
actual amount of chromium present in them after possible losses by volatilization during the fusion. They were pulverized in a “diamond steel” mortar to pass a 200-mesh sieve, and were carefully gone over with a magnet to remove any particles of steel (4). Samples varying from 0.3 to 4.0 grams in weight were then fused in a platinum crucible with fifteen times their weight of potassium hydrogen sulfate, The fusions were taken up in nitric acid (1:2), oxidized with sodium bismuthate in the usual way (S),and titrated with 0.01 N potassium permanganate and FeS04.(NH4)SO4.6H20. The fusions in nearly all cases were complete the first t h e , but occasionally a small insoluble residue had to be re-fused with potassium acid sulfate before oxidation and titration. The results of these analyses are given in Table 11. The pulverized rubies were next examined spectrographically to determine the sensitivity and persistence of the chromium lines when alumina played the role of solvent. The powders were loaded onto the electrodes from a small hole bored in the end of a brass rod; from the average of a number of weighings, this hole was found to deliver a sample of ruby weighing 0.0063 gram. The sample was spread evenly over the lower electrode to ensure as complete volatilization as possible of all the material during the time of photographic exposure. The results of the observations are recorded in Table 111. A comparison of Table I11 with Table I will point out the fact that the sensitivity of the spectral reaction of chromium was much greater in the case of the synthetic rubies than in the case of chromium trioxide. The least recognizable quantity of chromium when introduced in the arc as chromic acid was 0.001 mg., but the same element in fused alumina was recognizable to the extent of 0.00006 mg. Spectrographic Estimation of Chromium in Natural Rubies
Eight natural rubies from five different localities were subjected to arc excitation in the manner described in connection with the synthetic rubies. In each case about
13
6 mg. of pulverized ruby were used and the chromium was estimated from the number as well as from the intensity of spectral lines, by comparing the speatrograms with the “standards” used in compiling Table 111. The results of this examination are recorded in Table IV. Table IV-Spectrographic
3
4 5
7 8
Rubies
WEIGHT OB ESTD. CHROMIUMCHROMIUM (estd in 6 mg. of ruby) Mg. % Dark red crystal, gem Mysore, India variety 0 006 0.1 Red crystals, transMysore, India lucent 0 006 0.1 0 0006 0.01 Macon County, N. C. Pink, translucent Ural Mountains Deep red crystals, translucent 0.006 0.1 Mysore, India Deep red crystals, translucent 0 006 0.1 Zoutpansberg, vaal Trans- Deep opaque red crysta1* 0.006 0.1 Macon County, N. e. Deep red crystal, translucent 0 002 0 03 Ceylon Bright red, transparent 0.006 0.1 PLAcEoPoRIGIN
2
Estimation of Chromium in Natural DESCRIPTION
To check the reliability of the spectrographic method for estimating chromium in rubies, rubies Nos. 4 and 5, of which the writers had sufficient quantities, were examined by the procedure used for determining chromium in the synthetic rubies. The chromium content of ruby No. 4 was found to be 0.120 per cent, and of ruby No. 5, 0.159 per cent. Literature Cited (1) Doelter, Silsb. Akad. Wiss. Wien, 117 [ l ] , 819 (1908). (2) Doelter and Leitmeier. “Handbuc h der Mineralchemie,” Vol. 111, Pt. 2, p. 443, Leipzig, 1924. (3) Mahin, “Quantitative Analysis,” p. 467, New York, 1924. (4) Moses, A m . J . Sci., [a] SO, 271 (1910). (6) Papish, Econ. Geol., 2S, 660 (1929). (6) Papish, Brewer, and Halt, J . Am. Chem. Soc., 89, 3028 (1927). (7) Papish and Holt, Z . anoig. Chem., 192, 90 (1930). (8) Wild and Klemm, Cenlr. Mineral. Geol., 1926A, 20. (9) W6hler and Kraatz-Roschlau, Tschamak’s mineral. 9ctrog. MiU., 18, 456 (1899).
Elimination of Sulfur in Carbon Determinations b y Direct Combustion‘ Wm..H. Blatchley 4600 JONATBON ST., DEARBORN, MICH.
N VIEW of the frequency of erroneous results in carbon determinations owing to the influence of sulfur, the discussions of the subject in the textbooks on steel analysis seem wholly inadequate, if not positively misleading. A manufacturer of laboratory equipment has recently introduced a special carbon train designed for the elimination of sulfur. It involves the use of an electric heating unit and a catalytic cell for the conversion of sulfur dioxide to sulfur trioxide, followed by the usual zinc tower for its absorption. The author of one of the well-known textbooks, in his latest edition, just off the press, recommends the use of red lead for all carbon determinations by combustion in steel, pig iron, and graphite, the context indicating that the object is to insure complete combustion of the carbon. In another paragraph he mentions the necessity, when dealing with materials containing an unusual amount of sulfur, of using an additional bubble tube or jar filled to a depth of 2 inches with a concentrated solution of potassium permanganate, to 1
Received September 29, 1930.
absorb “most of the unusual amount of sulfur dioxide which is formed.” In a series of experiments recently carried out by the writer, it was found that, under certain conditions, the sulfur can be effectively eliminated without recourse to any special additions to the conventional carbon train, even when igniting ferrous sulfide containing 27.4 per cent of sulfur. The conditions under which this can be accomplished are as follows: The combustion tube is loosely packed in its outlet end with ignited asbestos which must extend into the hot part of the tube. After a few charges have been ignited in the tube with red lead flux, the asbestos becomes impregnated with a sublimate of this material. This is enough to oxidize to sulfur trioxide and fix in the form of lead sulfate the sulfur dioxide evolved by the average steel sample, whether a flux is used on the sample or not. If, then, red lead flux is used on pig irons and other high sulfur-bearing materials, the same reaction takes place in the combustion boat, and the effluent gases are free from sulfur dioxide.
